Abstract

A diverse number of reactant/catalyst systems have been investigated utilizing inelastic electron tunneling spectroscopy (IETS) to probe the vibrational structures of the various surface species. Catalytic systems studied were selected for their relevance to important industrial reactions, as well as to demonstrate the versatily of IETS and to expand the range of its known applications. These studies include observation of an ethoxide-to-acetate transformation above 470K for ethanol on alumina, demonstrating that IETS can effectively monitor surface reactions. Unique characterization of surface acetates formed on alumina by ethanol, acetic acid and acetaldehyde is obtained via analysis of IET spectra, as is information on the initial adsorption mechanism for each of the three species. Results obtained for ethanol adsorption on alumina-supported silver particles extend the use of IETS into new areas of supported metal catalysis. Characterization of the silver particles was accomplished utilizing transmission electron microscopy. Most significant, perhaps, are the studies of Zr(BH4)4 supported on aluminum oxide. This is the first reported instance of IETS being utilized to characterize the structure of a supported complex; and, indeed, represents one of the few structural studies performed thus far for this increasingly important class of catalysts. Interactions of ethylene, acetylene and propylene with the Zr(Bh4)4/Al2O3 (a known polymerization catalyst under certain conditions) were examined with the resultant observation of polyacetylene formation. The alumina films utilized in IETS studies were characterized by X-ray photoelectron spectroscopy to facilitate comparisons to actual commercial aluminas.